This invention relates to a head feeding mechanism of a magnetic head actuator assembly for use in a linear magnetic tape storage system represented by a DLT (digital liner tape) or a LTO (linear tape open) and, in particular, to a head feeding mechanism which is capable of assuring a stable tape contact force and of avoiding tape backlash with a simple and inexpensive mechanism and which is low in cost and small in number of assembling steps.
A linear magnetic tape storage system (magnetic recording/reproducing apparatus) of the type has been developed as a backup for a memory device (e.g. a hard disk) of a computer system. Various types of linear magnetic tape storage systems have already been proposed. For example, a digital linear tape drive as a DLT is disclosed in U.S. Pat. No. 5,862,014.
The digital linear tape drive (which may simply be called “tape drive”) is adapted to receive a tape cartridge having a single reel (supply reel) and contains a take-up reel in the interior thereof. When the tape cartridge is loaded in the tape drive, a magnetic tape is pulled out of the tape cartridge and taken up by the take-up reel through a head guide assembly (HGA). The head guide assembly serves to guide the magnetic tape pulled out of the tape cartridge to a magnetic head. The magnetic head exchanges information between the magnetic tape and the magnetic head. The head guide assembly generally comprises a boomerang-shaped aluminum plate and six large guide rollers each of which comprises a bearing.
The head guide assembly is also called a tape guide assembly and is disclosed, for example, in U.S. Pat. No. 5,414,585. An example of the guide roller is disclosed in Japanese Unexamined Patent Publication No. 2000-100025 (JP 2000-100025 A).
As disclosed, for example, in U.S. Pat. No. 5,793,574, the tape drive is generally comprised of a rectangular housing that has a common base. The base has two spindle motors (reel motors). The first spindle motor has a spool (take-up reel) permanently mounted on the base. The spool is dimensioned to accept a relatively high speed streaming magnetic tape. The second spindle motor (reel motor) is adapted to accept a removable tape cartridge. The removable tape cartridge is manually or automatically inserted into the drive via a slot formed on the drive's housing. Upon insertion of the tape cartridge into the slot, the tape cartridge engages with the second spindle motor (reel motor).
Prior to rotation of the first and the second spindle motors, the tape cartridge is connected to the permanently mounted spool (take-up reel) by means of a mechanical buckling mechanism. A number of rollers (guide rollers) positioned intermediate the tape cartridge and the permanently mounted spool guide the magnetic tape as it traverses at relatively high speeds back and forth between the tape cartridge and the permanently mounted spool.
The digital linear tape drive having the above-mentioned structure requires a pulling apparatus for pulling the magnetic tape from the supply reel to the take-up reel. Such a pulling apparatus is disclosed, for example, in International Publication No. WO 86/07471. According to WO 86/07471, take up leader means (first tape leader) is coupled to the take-up reel while supply tape leader means (second tape leader) is fixed to the tape on the supply reel. The first tape leader has a mushroom-like tab formed at its one end. The second tape leader has a locking hole. The tab is engaged with the locking hole.
Furthermore, a mechanism for joining the first tape leader to the second tape leader is required. Such a joining mechanism is disclosed, for example, in International Publication No. WO 86/07295.
Japanese Unexamined Patent Publication No. 2000-100116 (JP 2000-100116 A) discloses “Structure of Leader Tape Engaging Part”. In this structure, an end of a leader tape (second tape leader) can be locked to a tape end hooking part of a tape cartridge without requiring a tab projecting on a lateral side of the leader tape.
U.S. Pat. No. 5,857,634 discloses a locking system for preventing the rotation of a take-up reel of a tape drive when a tape cartridge is not inserted into the drive.
On the other hand, an example of the tape cartridge to be received in the digital linear tape drive is disclosed in Japanese Unexamined Patent Publication No. 2000-149491 (JP 2000-149491 A).
U.S. Pat. No. 6,241,171 discloses a tape drive in which a tape leader can be urged from a tape cartridge through a tape path to a take-up reel without using a buckling mechanism or a take-up leader.
The tape drive further comprises a magnetic tape head actuator assembly. The magnetic tape head actuator assembly is positioned between the take-up spool and the tape cartridge along a tape path defined by a plurality of rollers. During operation, the magnetic tape streams back and forth between the take-up spool and the tape cartridge, coming into close proximity to the magnetic head actuator assembly while streaming along the defined tape path. An example of such a magnetic tape head actuator assembly is disclosed in the above-mentioned U.S. Pat. No. 5,793,574.
Referring to FIG. 1, description will be made of the structure of an existing tape drive comprising a magnetic head actuator assembly. FIG. 1 is a plan view of the existing tape drive in the state where an upper cover is removed.
The tape drive 110 is adapted to receive a removable tape cartridge (not shown) and includes a take-up reel 111 in the interior thereof. The take-up reel 111 may be called a spool. The tape drive 110 comprises a generally rectangular housing (gear chassis) 112 having a common base. The base of the housing 112 has two spindle motors (reel motors) 113 and 114. The first spindle motor 113 has the take-up reel 111 permanently mounted to the base. The take-up reel 111 is dimensioned so as to accept a magnetic tape (not shown) streaming at a relatively high speed. The second spindle motor 114 is adapted to receive the removable tape cartridge. The removable tape cartridge is manually or automatically inserted into the tape drive 110 via a slot 1121 formed on the housing 112 of the tape drive 110 along the extending direction of the slot 1121.
When the tape cartridge is inserted into the slot 1121, the cartridge is engaged with the second spindle motor 114. Prior to rotation of the first and the second spindle motors 113 and 114, the tape cartridge is connected to the permanently mounted take-up reel 111 by means of a mechanical buckling mechanism. A number of rollers (guide rollers) 115 are positioned between the tape cartridge and the take-up reel 111 and guide the magnetic tape as it streams at a relatively high speed back and forth between the tape cartridge and the permanently mounted take-up reel 111.
The housing 112 is made of aluminum die-casting which is a non-magnetic material. Accordingly, the second spindle motor 114 is covered with a plate 116 of an iron-based magnetic material in order to inhibit magnetic leakage from a magnet (not shown) of the second spindle motor 114.
The tape drive 110 further comprises a magnetic tape head actuator assembly (hereinafter may be simply called “actuator assembly”) 120. The actuator assembly 120 is positioned between the take-up reel 111 and the tape cartridge along a tape path (not shown) defined by the rollers 115. During operation, the magnetic tape streams back and forth between the take-up reel 111 and the tape cartridge, coming into close proximity to the actuator assembly 120 while streaming along the defined tape path.
The actuator assembly 120 is disposed on the base of the housing 112 and has a magnetic head assembly 130 (see FIG. 2) moving along and in proximity of a magnetic tape surface. The magnetic head assembly 130 may hereinafter be abbreviated “head assembly”. On the base of the housing 112, a guide bar 117 is arranged to guide the head assembly 130 moving up and down in a direction perpendicular to the base of the housing 112.
Referring to FIGS. 2 to 4, description will be made of the structure of the actuator assembly 120.
FIG. 2 is a perspective view showing the actuator assembly 120. FIG. 3 is an exploded perspective view showing the actuator assembly 120 of FIG. 2, in which the actuator assembly is shown disassembled into the head assembly 130 and a head feeding mechanism 140 with the head feeding mechanism 140 further disassembled into a rotating part and a vertically moving part. FIG. 4 is a sectional view taken along a line A—A in FIG. 1.
As shown in FIG. 2, the actuator assembly 120 comprises the head assembly 130 and the head feeding mechanism 140. Herein, the vertical direction is a direction perpendicular to a plane of the base of the housing 112 in FIG. 1, i.e., the extending direction of the guide bar 117.
The head assembly 130 comprises a magnetic head 131 extending in the vertical direction, a head holder 132 holding the magnetic head 131 on its one side surface (hereinafter may be called “front surface”), and a pair of flexible printed circuits (hereinafter may be abbreviated to “FPC”) 133. The FPCs 133 extend at the opposite side surface (hereinafter may be called “rear surface”) to electrically connect the magnetic head 131 and an external circuit (not shown).
The head holder 132 comprises a head mounting portion 1321 and a pair of flanges 1322. On the head mounting portion 1321, the magnetic head 131 is mounted. The flanges 1322 extend rearward from opposite sides of an upper end of the head mounting portion 1321 in a direction perpendicular to the head mounting portion 1321 and are in parallel to each other. Each of the flanges 1322 has a screw hole for receiving a screw 134. By screwing screws 134 to a head lift 142 of the head feeding mechanism 140 through the screw holes, the head assembly 130 is coupled to the head lift 142 of the head feeding mechanism 140. The head mounting portion 1321 has an opening formed at the center thereof and behind the magnetic head 131 mounted thereon. Through the opening, one ends of the FPCs 133 are electrically connected to the magnetic head 131.
On the rear side of the head holder 132, the head feeding mechanism 140 is disposed with a lead screw 141 having a rotation center axis extending in the vertical direction. The head lift 142 of the head feeding mechanism 140 is engaged with the lead screw 141 and moves the head assembly 130 up and down following the rotation of the lead screw 141.
Referring to FIG. 3, description will be made of the head feeding mechanism 140.
The head feeding mechanism 140 comprises the lead screw 141, the head lift 142, a split nut 143, and a lead screw gear 144. The lead screw 141 is provided with an external thread and has a rotation center axis extending in the vertical direction. The head lift 142 has a generally rectangular shape with an opening formed at its center. The head lift 142 holds the head assembly 130 and moves the head assembly 130 up and down. The split nut 143 is located in the opening of the head lift 142 and fixed to the head lift 142. The split nut 143 has an internal thread 1431 to be engaged with the lead screw 141. The lead screw gear 144 is fixed to a lower end of the lead screw 141 to rotate the lead screw 141 around the rotation center axis when it is driven by another driving means (not shown). As a result, following the rotation of the lead screw 141 around the rotation center axis, the split nut 143 moves the head lift 142 in the vertical direction, i.e., the extending direction of the rotation center axis.
The head lift 142 has a bottom portion 1421 on the side of the lead screw gear 144, a pair of side wall portions 1422 extending upwards from opposite ends of the bottom portion 1421 and in parallel to each other, and a top portion 1424 bridging the side-wall portions 1422 at their upper ends. The bottom and the top portions 1421 and 1424 have circular openings formed at their centers, respectively. In the circular openings, bearings 145 and 146 for the lead screw 141 are disposed, respectively. The side wall portions 1422 have upper surfaces provided with screw holes 14221 to be engaged with the screws 134. Furthermore, the side wall portions 1422 are provided with nut holding grooves 14222 formed on inner surfaces of the side wall portions 1422 at positions near to the upper ends to hold the split nut 143.
The head lift 142 has a projecting portion 1425 formed on one of the side wall portions 1422 to project laterally outwards from the lower end thereof. The projecting portion 1425 has a guide groove for receiving a guide 147. The guide 147 is attached to the guide bar 117 (see FIG. 1) to be slidable in the vertical direction along the guide bar 117. The guide 147 serves to prevent the head lift 142 from rotating around the rotation center axis.
The split nut 143 has a pair of splits (slits) 1432 (only one being illustrated in the figure) oriented parallel to the rotation center axis and circumferentially spaced by 180 degrees from each other. The split nut 143 further has a pair of projections 1433 formed at its upper end to extend laterally outwards. The projections 1433 are fitted to the nut holding grooves 14222 of the side wall portions 1422. Thus, the internal thread 1431 of the split nut 143 is engaged with the external thread of the lead screw 141 so that the head lift 142 can be moved in the vertical direction along the rotation center axis of the lead screw 141 following the rotation of the lead screw 141.
The split nut 143 further has an annular groove formed on its outer periphery. A doughnut spring (ring spring) 148 is positioned in the annular groove. The doughnut spring 148 is a special coil spring formed into a doughnut-like shape. The doughnut spring 148 applies an inwardly directed adaptive compressive force on the split nut 143.
In the above-mentioned structure of the actuator assembly 120, the lead screw 141 of the head feeding mechanism 140 can rotate clockwise or counterclockwise. In this event, the head lift 142 and the head assembly 130 attached thereto move in the vertical direction along the rotation center axis following the rotation of the lead screw 141.
A combination of the split nut 143 and the doughnut spring 148 serves as a backlash preventing mechanism for eliminating backlash of the head lift 142, and therefore, of the actuator assembly 120. More in detail, in order to prevent the backlash of the head lift 142 with respect to the lead screw 141 during movement of the head lift 142 following the rotation of the lead screw 141, the doughnut spring 148 elastically deforms and inwardly presses the split nut 143 having the splits (or slits) 1432 to the lead screw 141.
The split nut is often subjected to mechanical shock, which causes the backlash in the actuator assembly. U.S. Pat. No. 5,793,574 mentioned above discloses an actuator assembly using a shock suppression sleeve. The shock suppression sleeve improves the resistance against backlash due to mechanical shock, or loose play resulting from wear or mechanical tolerances. It is noted here that the shock suppression sleeve also comprises a combination of the split nut and the doughnut spring and is applied to the magnetic head actuator assembly.
As will be understood from FIG. 4, the lead screw 141 has a lower end portion rotatably supported by the housing 112 through a bearing 151. The lead screw gear 144 is mounted on the bearing 151 through a washer 152 and a lift spring 153. The lead screw 141 has an upper end portion rotatably supported by a bearing holder 156 through another bearing 155. The bearing holder 156 is fixedly mounted on the housing 112. An E ring 157 is interposed between the bearing 155 and the external thread of the lead screw 141.
As described above, the existing magnetic head actuator assembly includes a combination of the split nut 143 and the doughnut spring 148 as the backlash preventing mechanism. However, each of the split nut 143 and the doughnut spring 148 has a special shape or structure and is therefore high in cost. Furthermore, it is difficult to obtain a stable inwardly directed pressing force applied to the lead screw 141 because of variation in elastic force of the split nut 143 and the doughnut spring 148.
In the existing head feeding mechanism 140, the split nut 143 for moving the head lift 142 following the rotation of the lead screw 141, the bearing 145 for the lead screw 141, and the guide 147 for inhibiting the rotation of the head lift 142 are formed as separate components. Therefore, the existing head feeding mechanism 140 is high in cost and is difficult to be assembled.